Вызов subject.onNext () внутри doOnSubscribe

Почему вызов subject.onNext(o) внутри doOnSubscribe не дает никакого эффекта, однако вызов subject.onComplete() приводит к завершению потока !?

final PublishSubject<Integer> subject = PublishSubject.create();

    final Observable<Integer> observable = subject.doOnSubscribe(new Consumer<Disposable>() {
        @Override
        public void accept(@NonNull Disposable disposable) throws Exception {
            System.out.println("disposable = [" + disposable + "]");
            subject.onNext(1);
            //or
            Observable.just(2, 3).subscribe(subject);
        }
    });

    observable.subscribe(new Observer<Integer>() {
        @Override
        public void onSubscribe(Disposable d) {
            System.out.println("d = [" + d.isDisposed() + "]");
        }

        @Override
        public void onNext(Integer integer) {
            System.out.println("item = [" + integer + "]");
        }

        @Override
        public void onError(Throwable e) {
            System.out.println("e = [" + e + "]");
        }

        @Override
        public void onComplete() {
            System.out.println("onComplete");
        }
    });/*
    expected:
    disposable = [false]
    d = [false]
    item = 1
    item = 2
    item = 3
    onComplete
    but received :
    disposable = [false]
    d = [false]
    onComplete
    */